The present invention relates to a developing method and a developing apparatus, and more particularly, to a method and developing apparatus for performing a developing process by applying developing solution to a surface of a substrate such as a semiconductor wafer.
To manufacture a semiconductor device, photolithography technique is used. In the photolithography technique, photoresist is coated on a semiconductor wafer, thereby forming a photoresist film on one surface of the wafer. The photoresist film is exposed to a predetermined circuit pattern and then developed. Thus, a predetermined pattern photoresist film is formed on the wafer.
In general, the wafer is developed in the following manner. First, the developing solution is continuously applied from a nozzle to the photoresist film to which the circuit pattern has been exposed. The applied developing solution forms a layer, which contacts that surface of the photoresist film. The layer of developing solution is maintained on the resist film for a prescribed time, by continuously applying the developing solution.
Recently, a linear nozzle 100 of the type shown in FIG. 7 is used to apply developing solution in order to save the developing solution and to apply a developing solution uniformaly over an entire surface of the wafer. The linear nozzle 100 has a number of discharge holes 101 arranged in a straight line. To develop the resist film formed on a wafer 102, the nozzle 100 is moved to face the wafer 102. The nozzle 100 applies the developing solution through the holes 101 onto the wafer 102, in the form of parallel streams. When the streams of developing solution merge on the surface of the resist film to form a film-like stream, then, the wafer 102 is slowly rotated by 180.degree.. After the developing solution layer covers the entire surface of the resist film, the rotation speed of the wafer 102 is increased.
The conventional method of developing the resist film by the use of the linear nozzle 100 is, however, disadvantageous in the following respects:
(1) It takes some time until the developing solution 103 spreads all over the pattern-forming surface of the wafer 102. This is because the wafer 102 is rotated only after the developing solution 103 is applied onto the resist film. Consequently, that part of the resist film, which first contacts the developing solution 103 may differ from any other part of the resist film in terms of resolution. PA1 (2) Second, much attention must be now pad to the influence of the first impact given by the developing solution 103 that first contacts the resist film.
To be more specific, the parallel streams of developing solution 103 applied through the holes 101 merge together on the resist film, forming a film-like stream. The wafer 100 must be rotated only after the developing solution forms a film-like stream. It is therefore impossible to rotate the wafer 102 before or at the same time the developing solution 103 first contacts the photoresist film. As a consequence, that part of the resist film, which first contacts the solution 103, may be developed to excess, unlike any other part of the resist film.
That is, when the valve connected to the linear nozzle 100 is opened to supply the developing solution 103 to the nozzle 100, the pressure on the solution 103 increases momentarily. Thus, the streams of developing solution applied from the nozzle 100 give the first impact to the wafer 102. Consequently, that part of the resist film, which first contacts the solution 103, is developed to excess, unlike any other part of the resist film.
The circuit patterns recently designed and formed on the wafer consist of very fine elements arranged in high density, and the resist film must be processed with high resolution. This is why the influence of the first impact, which has hitherto been neglected, now needs to be considered.
As described above, the conventional developing method is disadvantageous in view of the non-uniform development of the resist film, which results not only from the different timings of applying the developing solution to the resist film, but also from the influence of the first impact of developing solution.